The measurement methods of mineral magnetism can be divided into three categories: mass dynamic method, induction method and indirect method. Commonly used in mineral processing is the mass dynamic method, which is simple in installation and has sufficient sensitivity. For general conditions, a magnetic balance can meet the requirements. The kinetic method can be divided into the Gouy method and the Faraday method. The principle, instrumentation and analysis steps of the two methods for analyzing the magnetic susceptibility of magnetic minerals are described below.
1. The specific magnetic susceptibility of minerals measured by the Gouy method
This method is a method for directly measuring the specific magnetic susceptibility and is suitable for the determination of the specific magnetic susceptibility of ferromagnetic minerals and weak magnetic minerals.
Measuring device - measuring device and circuit as shown in Figure 4-5-10. It is mainly composed of analytical balance, thin-walled glass tube, multi-layer solenoid coil, DC ammeter, resistor and switch.
The principle of measurement is to hang a long sample of equal section at one end of the balance so that it is in a region where the magnetic field strength is uniform and high, and the other end is in a region where the magnetic field strength is low, and the sample is subjected to it in the magnetic field. The role of the magnetic force in the same length direction.
In the above formula, l, m, and g are known numbers, and the size of H1" is changed during the test. , you can find value. If the sample is long and the cross-sectional area is small, the demagnetization factor is small, and the object specific magnetic susceptibility of the sample can be used as the material specific magnetic susceptibility of the sample.
Method of Measurement - The mass of the glass tube was weighed prior to measurement, and the sample was placed in a glass tube and tamped to the desired extent. Weigh the sample and the quality of the glass tube, then hang the glass tube containing the sample under the left weighing pan of the analytical balance, so that its lower end is close to the center of the solenoid, the coil is connected to the current, and the current is measured at different currents. The amount of magnetic force the sample is subjected to. By substituting the measured data into the above formula, the specific magnetic susceptibility and specific magnetization of the mineral can be obtained, and the sum can be drawn.
In order to improve the accuracy of the measurement, when measuring weak magnetic minerals, the accuracy of the balance and current is required to be higher, the magnetic field strength should be appropriately increased, and the average is repeated 3 to 4 times.
2. Faraday method to measure the specific magnetic susceptibility of minerals
The Faraday method is generally used to determine the specific magnetic susceptibility of weak magnetic minerals. The main difference between this method and the ancient law is that the volume of the sample is small, so it can be approximated that the magnetic force is a constant in the space occupied by the sample. The principle of measurement is to measure the specific magnetic force of a mineral in an inhomogeneous magnetic field in which HgradH is known in advance, and then determine the specific magnetic susceptibility of the sample as follows:
The Faraday method can be used with different measuring devices, such as ordinary balances, Weiss balances, automatic balance balances, Kuli-Jinnai twist scales, Sukh Smith ring scales, Chevalier-Pier measuring instruments, etc. The accuracy of the ordinary balance method (ie, the magnetic balance method) is not high (the accuracy is only 10-6), but because of its simple structure, it is widely used in China. It uses the comparison method between the standard sample and the sample to be tested; The measurement accuracy can reach 10-6~10-8, which has become the main device for determining the specific magnetic susceptibility of minerals. It measures the absolute specific magnetic susceptibility. The measuring devices and steps can refer to the relevant literature.
(II) Analysis of magnetic mineral content
The magnetic analyzers such as magnetic separators, magnetic analyzers, induction roller magnetic separators, and strong magnetic mineral separators are used in the laboratory to analyze the content of magnetic minerals in the ore, determine the ore selection index of ore, and evaluate the process of the deposit. Check the operation of the magnetic separator and purify various single minerals for material composition, mineral composition, and selectivity. In particular, the need for ore and mineral products in magnetic separation plant Magnetic analysis, identification of tailings in metal loss and reason, in order to improve the process and magnetic targets. In the above magnetic analyzer, a magnetic separator is commonly used.
Analysis for the wet magnetic tube ferromagnetic mineral magnetic mineral content analysis apparatus, it is mainly the glass tube by a movable electromagnet and the electromagnet working gap, whose structure is shown in FIG 4-5-11. The electromagnet consists of a C-shaped core and a coil with an angle of about 90 at the end of the core. The conical pole, between the two poles is the working space of the magnetic tube. A frame made of a non-magnetic material with a transmission is fixed to the electromagnet, and the glass tube is embedded in a collet connected to the transmission. The glass tube is level 40. ~45. The angle can be moved up and down 40~50mm, and can be rotated at a small angle. The glass tube is open at one end for the entry of the sample and the rinse water, and the other end is tapered and sleeved with a rubber tube with a clamp. The clamp can adjust the water discharge amount, and the maximum magnetic field strength of the magnetic separation tube can reach 240 kA/m.
Firstly adjust the flushing water volume and the clamp so that the water surface in the magnetic separation tube is kept above 100 ~ 120mm above the magnetic pole; then turn on the DC power supply and start the transmission; then feed the sample into the magnetic separation tube, in the sample The ferromagnetic mineral is adsorbed on the inner wall of the tube near the magnetic pole, and the non-magnetic mineral is discharged from the lower end of the glass tube with the flushing water. The up and down movement of the glass tube and the left and right rotation facilitate the discharge of non-magnetic minerals. When the water in the tube is clear for 5 to 15 minutes, the sorting can be stopped. Close the clamp, cut off the current, and remove the magnetic material. The magnetic product and the non-magnetic product are clarified, dried, weighed, and the content of the magnetic product in the sample is calculated.
The sample should be ground to a size of 1 mm or less according to the mineral size of the mineral. The diameter of the magnetic tube is usually 5 ~ 10 g or 10 ~ 20 g.
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